1. Field of the Invention
The present invention relates to a wide bandgap semiconductor device, and in particular to a wide bandgap semiconductor device having a Schottky electrode.
2. Description of the Background Art
A Schottky barrier diode is a diode which applies a Schottky barrier formed by a junction between a metal and a semiconductor. The Schottky barrier diode has advantages that it has a small voltage drop in a forward direction, and that it can make a high-speed response. On the other hand, it has been conventionally known that the Schottky barrier diode has problems that it has a large leak current in a reverse direction, and that it has a low reverse-direction breakdown voltage. In order to solve these problems, Schottky barrier diodes having a structure in which a plurality of junction barriers are provided at a Schottky junction interface have been proposed. Such a Schottky barrier diode is called a junction barrier Schottky diode (JBS).
For example, Japanese Patent Publication No. 59-35183 describes a JBS having an n-type region, a p-type region surrounded by the n-type region except for its front surface, and a Schottky barrier metal layer which is in contact with both the n-type region and the p-type region. According to the JBS, the p-type region is arranged to suppress a reverse current which flows through the n-type region, the metal layer, and a pn junction formed by the n-type region and the p-type region when a reverse voltage is applied to the junction, using a space-charge region formed in then-type region.
Further, Japanese Patent Laying-Open No. 2009-140963 describes a JBS having a semiconductor substrate which has n-type semiconductor layer, a p-type semiconductor layer which constitutes a composite rectification region provided at a predetermined depth from a front surface of the n-type semiconductor layer, and a metal layer which is provided to be in contact with the n-type semiconductor layer and the p-type semiconductor layer. The JBS has a small leak current in the reverse direction, can save power, and can be driven with a low voltage.